Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | $ 3,033 | $ 1,727 |
| Balance at end of period | 981 | 2,076 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 143 | 25 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 915 | 1,034 |
| Payments for legal matters | (3,110) | (710) |
| U.S. Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 2,698 | 1,537 |
| Provision for legal matters | 894 | 1,019 |
| Payments for legal matters | (2,977) | (580) |
| Balance at end of period | 615 | 1,976 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 9 | 72 |
| Provision for legal matters | 21 | 15 |
| Payments for legal matters | (9) | (24) |
| Balance at end of period | $ 21 | $ 63 |